"Each person in the world (at least among the 1.59 billion people active on Facebook) is connected to every other person by an average of three and a half other people," write Sergey Edunov, Carlos Diuk, Ismail Onur Filiz, Smriti Bhagat, and Moira Burke, who conducted the study.

Estimated average degrees of separation between all people on Facebook. The average person is connected to every other person by an average of 3.57 steps. The majority of people have an average between three and four steps.Facebook

In the US, people are more closely connected — 3.46 degrees compared to 3.57 worldwide — according to the research.

Facebook's scientists created an algorithm to work out how separated its users are. The task was "monumental," according to the company, as "the number of people reached grows very quickly with the degree of separation."